This invention relates to sewing machines and, more particularly, to electronically controlled sewing machines.
Sewing machines employing sophisticated electronic technology for the storage and subsequent retrievel of stitch pattern information for a multiplicity of patterns have enjoyed great commercial success in recent years. One great advantage of the use of an electronically controlled sewing machine is in its simplicity of operation and control, as perceived by the user. With the recent availability of relatively low cost microcomputers, electronically controlled sewing machine incorporating such a device have greatly increased the versatility of control afforded to the sewing machine operator. However, due to the physical nature of the microcomputer it is limited in its memory capacity so that information for sewing only a preset number of patterns may be stored therein. Accordingly, it would be desirable to increase the memory capacity of an electronically controlled sewing machine. One way of doing this would be to provide a microcomputer having an increased memory capacity. However, this approach suffers from a number of disadvantages. For example, the information stored in the microcomputer is fixed and the only way to change it is to physically replace one microcomputer with another, a job which must be done by a highly skilled technician. A further disadvantage is that in order to provide the operator with a means for addressing all of the patterns stored in the microcomputer without exceeding the space available on the sewing machine for input selection switches, it has been proposed to utilize a numerical input. Unfortunately, such an approach is not desirable because it takes away from the simplicity of operation of the sewing machine which is a highly desirable advantage to the user.
Accordingly, it has been proposed to utilize plug-in modules containing additional patterns or programs to allow the sewing machine to have features which were not originally contained in the machine. The modules consist of read only memories which contain the required software to allow the machine to perform the new features. Unfortunately, since these modules are handled by unskilled consumers, there exists the possibility of the user damaging the module. While proper packaging of the module can minimize the chance of damage, it is important to verify that the contents of the module is undamaged before allowing the software in the module to be used. Additionally, if it is found that the module is damaged, the user should be made aware of the problem and should be prevented from using the module. In addition to the possibility of damage to the memory within the module, there also exists the possibility of damage to the transmission channel between the module and the internal microcomputer, such as may be caused by dirt or the like.
It is therefore a primary object of this invention to provide a method of checking the integrity of such a module as well as the transmission channels between the module and the internal microcomputer.